Principles of Disease and Epidemiology Ch 14 Diseases and US Pathogen a disease causing microbial growth or toxin Disease an abnormality in which the body or part is not properly adjusted The body part is overcome by the microbe Change in the state of health Infection is the invasion and growth of a pathogen in the body More words Host Is an organism that shelters and supports the growth of pathogens Pathology scientific study of disease Etiology cause of a disease Pathogenesis development of disease Is this a type of symbiosis Normal Microbiota In some cases it is normal for microbes to be growing Most mammals germ free in utero are colonized after birth Microbes that establish permanent colonies inside or on outside of the body without causing disease are called normal microbiota Transient microbiota are microbes that are stable for a time then disappear Symbiosis With normal microbiota usually both species benefit from this arrangement Normal microbiota can prevent infections may make necessary vitamins in return for nutrients form the host is called Opportunistic microbes may cause disease under certain instances Probiotics are live microbes applied to or ingested into the body intended to exert a beneficial effect Normal Microbiota on the Human Body Table 14 1 Skin Propionibacterium acnes Staphylococcus epidermidis Staphylococcus aureus Candida spp Most microbes are transient on skin Why Eyes Basically the same as that found on the skin Eyes have lysozyme few nutrients washing by tears Nose and throat S aureus S epidermides Streptoccoccus pneumoniae Haemophilus Neisseria Mouth Streptoccoccus Lactobacillus Actinomyces Bacteroides Fusobacterium Treponema Cornebacterium Candida Over 200 species Idea environment Is a diverse environment How do we know what lives in the mouth Large intestine Bacteroides Fusobacterium Lactobacillus Enterococcus Escherichia Enterobacter Proteus Klebsiella Shigella Candida Is essentially a chemostat Has a large resident microbiota Urogenital system Staphylococcus epidermidis Enterococcus Lactobacillus Pseudomonas Klebsiella Proteius In urethra Lactobacilli Streptococcus Staphylococcus Bacteroides Clostridium Candida albicans Trichomonas vaginalis in vagina is acidic Koch s postulates Same pathogen must be present in every case of the disease Pathogen must be isolated in pure culture Pathogen isolated from pure culture must cause the same disease in a healthy susceptible laboratory animal Pathogen must be isolated from this animal Exceptions to Koch s postulates Are modified to establish etiologies of diseases caused by viruses and fastidious bacteria which cannot be grown on defined media Some diseases are caused by a variety of microbes Some diseases such as S pyogenes can cause several different diseases Some diseases can only occur in one organism so we cannot run the full Koch s postulates Why Disease classification and codification Vocab Measurements Recognition and patterns Symptoms change in body function Diagnosis identification Sign a measurable change Syndrome a specific group of symptoms or signs that always accompanies a specific disease Communicable diseases transmitted directly or indirectly from one host to another Contagious disease is easily spread from one person to another No communicable diseases are caused by microbes that normally grow outside the body and are not transmitted from one host to another Clostridium tetani Where how bad and how much Words to describe ID Incidence number of people contracting the disease Prevalence number of cases at a particular time Frequency is in terms of sporadic endemic epidemic and pandemic Acute chronic subacute and latent Herd immunity is the presence of immunity in most of the population Local infection affects a small area of the body Systemic infection spread throughout the body Bacteremia bacteria in the blood Septicemia bacteria multiply in blood Secondary infections occur after a host is weakened from a primary infection Subclinical cannot be measured Severity or Duration of a Disease Acute disease Symptoms develop rapidly Chronic disease Disease develops slowly Subacute disease Symptoms between acute and chronic Latent disease Disease with a period of no symptoms when the patient is inactive Recognition and patterns of disease Predisposing factors make the body more susceptible to disease they include Gender Climate Age Fatigue Nutrition Lifestyle Drug treatments What happens when a disease does occur Incubation period is the time between the initial infection and the first appearance of signs and symptoms Prodromal period is the first mild signs and symptoms Illness is when the disease is at its height Decline signs and symptoms decline Convalescence time until the body returns to predisease state The Stages of a Disease Figure 14 5 Spreading of Infection Reservoir of infection provides pathogen with conditions for survival Human carriers asymptomatic or latent Animal zoonoses various routes Nonliving Reservoirs water fertilizer ect Transmission of Disease Contact transmission Direct person to person transmission Indirect contact transmission of Disease Fomite aTransmission nonliving transfer 1 meter soiled goods Droplet transmission over short distances Vehicle transmission water food air Vectors mechanical or biological Transmission of Disease Figure 14 6a 8 Portals of entry and Exit Pathogens have preferred portals of entry and exit Most common portals Respiratory tract Gastrointestinal tract Urogenital tract Blood to blood Transmission of Disease Vehicle Transmission by an inanimate reservoir food water Vectors Arthropods especially fleas ticks and mosquitoes Mechanical Arthropod carries pathogen on feet Biological Pathogen reproduces in vector Nosocomial Hospital acquired infections 5 15 get infections while in the hospital Microbes in hospital Chain of transmission Compromised host Is a hospital the best place to be if you are sick Nosocomial Hospital Acquired Infections Are acquired as a result of a hospital stay 5 15 of all hospital patients acquire nosocomial infections Figure 14 7 9 Nosocomial Infections ANIMATION Nosocomial Infections Overview Table 14 5 Common Causes of Nosocomial Infections Percentage of Total Infections Percentage Resistant to Antibiotics Coagulasenegative staphylococci 25 89 S aureus Enterococcus Gram negative rods 16 10 23 80 29 5 32 C difficile 13 None MRSA USA100 92 of health care strains USA300 89 of community acquired strains Clinical Focus p